The invention involves a process for feeding dispersible solid fuels, such as coal dust, into the calcinator of a system for manufacturing cement clinkers made of cement raw meal, which is preheated in a heat exchanger system, calcinated in the calcinator provided with the fuel and baked into cement clinker in a rotary tubular kiln, whereby the pre-heated cement raw meal is fed into the reaction section of the calcinator via a meal intake box that has a sloping raw meal chute and deflector slide and is arranged on the outside of the calcinator and connected to it through a wall opening. In addition, the invention involves a device for performing the process.
Cement clinker production lines of the type named above must be able to generate, in the calcinator equipped with a secondary firing (in addition to the rotary kiln firing), a high-grade calcinated raw meal prior to introduction into the rotary tubular kiln. In the process, large quantities of fuel must be burned in the calcinator, in order to be able to perform the highly exothermic calcination reactions (specific heat consumption 550 kcal/kg clinker at a total heat consumption of approx. 800 kcal/kg cement clinker). As a calcinator reactor, the rotary kiln exhaust gas line that ascends at first in a manner that approaches vertical is used, which usually is deflected by 180° into a descending pipeline branch, which opens into the lowermost cyclone of the cyclone suspension-type heat exchanger system for the purpose of separating the calcinated raw meal from the exhaust gas stream.
The pre-heated raw meal from the next to last cyclone stage of the cyclone suspension-type heat exchanger system and the calcinator fuel are fed, into the reaction section of the rotary kiln exhaust gas channel, the fuel combusting with excess oxygen out of the rotary kiln exhaust gas and/or with the oxygen from the tertiary air introduced from the clinker cooler. Last, but not least for cost considerations, the calcinator fuel often consists of dispersible solid fuels such as coal dust, for example, which is blown in via a pipeline into the reaction section of the calcinator.
For a uniform progression of the combustion reaction and the calcination reaction running parallel to it, a uniform distribution of the raw meal and the fuel in the reaction section of the calcinator is important. Of course, developmental efforts have been focused on distributing the pre-heated cement raw meal out of the second lowest cyclone stage of the cyclone suspension-type heat exchanger system uniformly over the cross-section of the reaction section of the calcinator, whereby the pre-heated raw meal is introduced into the reaction section of the calcinator via a meal intake box that has a sloping raw meal chute and an adjustable deflector slide and is arranged on the outside of the calcinator and connected to it through a wall opening (Publication “KHD SYMPOSIUM '92 Volume 2 Modem Combustion Technology” of the KHD Humboldt Wedag AG company, 1993, Article “Development Trends in the Clinker Combustion Process” by C. Bauer, pages 11 to 15, FIG. 3). However, it has been observed that when, as has been customary until now, the coal dust injection point of the calcinator reactor is arranged displaced opposite from or at least to the side of the raw meal feed point and the solid fuel is not optimally distributed over the cross-section of the calcinator, the danger can not be ruled out that an open flame occurs on the coal dust injection point in the calcinator (also see DE-B-25 10 312), which leads to local overheating with material molten phase formation and undesired material caking, i.e., it was thus far not always ensured that the solid fuel, such as coal dust, for example, oxidizes and/or bums in a flameless manner in the gas-raw meal suspension.